Download Control Systems

Control Systems
By
M. Asim Rehmat
Lecturer CS&E Department,
UET Lahore
Introduction
• Muhammad Asim Rehmat
• MS Computer Science in Artificial Intelligence, UET
Lahore
• Belongs to SIALKOT and Engaged.
• Got 1st prize in All Pak E-Club Project Exhibition
• Got 1st prize in Final Year project Evaluation
• Team Lead of Database section and Servers in the
Development of PAK Linux at UET
• Got more than 8 First prizes in All Asia and All Pakistan
Engineering & Software Competitions as Project Advisor
• Subjects I Teach are:
• Robotics & CNC Machines, Embedded Systems,
Industrial Automation, Control Systems, Artificial
Intelligence
Course Plan
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2 Assignments
10
1 Quiz
10
Mid-Term
30
Final
40
Term Project
50
Viva
20
Lab Performance 20
Personal/Professional Growth
20
Course material
• Lecture slides
• Text Book: Control Systems
Engineering by Norman S. Nise, John
Wiley, Asia, 4th edition, 2004.
• Reference Book: Electronics Circuits
Fundamentals by Franco, Oxford
University Press, 1997.
• WWW
What is a Control System?
A Control System consists of subsystems and
processes (or plants) assembled to control the
outputs of a process.
Typical Examples
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Central Temperature Control
Fluid Level maintenance systems
Battery Voltage Control
Human has numerous control systems
built in it.
Control System another view
• A Control System is an arrangement of
physical components connected/related in
such a manner as to command, direct or
regulate itself or another system.
Human like Control
How….. Control Systems in
Robotics Perspective
Autonomous planning and Exploration
Autonomous control
Industry
…….…Everywhere
Control systems are divided into
two classes:
a) If the aim is to maintain a physical variable at some fixed
value when there are disturbances, this is a regulator.
Example: speed-control system on the ac generators of
power utility companies.
b) The second class is the servomechanism. This is a
control system in which a physical variable is required to
follow (track) some desired time function.
Example: an automatic aircraft landing system, or a robot
arm designed to follow a required path in space.
Advantages of a Control System
• Power amplification
– Radar antenna positioned by the low-power
rotation of a knob at the input, requires a large
amount of power for its output rotation.
Control system will produce the needed
power amplification/power gain.
Advantages of a Control System
• Remote control
Rover was built to
work in contaminated
areas at Three Mile
Island where a
nuclear accident
occurred in 1979.
Advantages of a Control System
• Convenience of input form
– In a temperature control system, the input is
the position on a thermostat and the output is
the heat. Thus a convenient position input
yields a desired thermal output.
Advantages of a Control System
• Compensation for disturbances
– In an antenna system that points in a
commanded direction, wind can force the
antenna to deviate from commanded
direction. The system should detect the
disturbance and act accordingly.
Classical Control Systems
• Liquid Level Control
Response Characteristics
• Consider a control system for an elevator.
– The input is a step function instructing the
elevator to go to a higher floor (4).
– The output is a transient response plus a steadystate response and has a steady-state error.
Open-Loop Systems
• An open-loop system cannot compensate
for any disturbances that add to the
controller’s driving signal or to the process
output.
Closed-Loop (Feedback Control)
• A closed-loop system can compensate for
disturbances by measuring the output,
comparing it to the desired output, and driving
the difference toward zero.
Closed-Loop (Feedback Control)
Closed-Loop (Feedback Control)
• Greater accuracy than open-loop systems
• Transient and steady-state responses can be
controlled more easily
• More complex and expensive than open-loop
systems
– Requires monitoring the plant output
Analysis and Design Objectives
• Transient Response must meet certain criteria.
Hard disk read write etc.
• Steady-State Response must meet certain
criteria.
• The system must have Stability.
–
Total Response = Natural Response +
Forced Response
• Natural response describes the way the system
dissipates or gain energy. It is dependent only on
the system not the input
• Forced response depends on the input.
• Natural response must go to zero leaving only the
forced response or oscillate
Analysis and Design Objectives
• Other Considerations
– Hardware limitations
– Finances
– Robust Design
Antenna Azimuth Position Control
Design Stages for the Antenna
Step-3: Draw Schematic
Step-4: Draw Block Diagram
Mathematical Models
• Model the system mathematically using
physical laws.
– Kirchoff’s Voltage Law - The sum of voltages around a closed
path is zero.
– Kirchoff’s Current Law - The sum of currents flowing from a node
is zero.
– Newton’s Laws - The sum of forces on a body is zero
(considering mass times acceleration as a force).
The sum of moments on a body is zero.
• The model describes the relationship
between the input and the output of the
dynamic system.
Step-5: Reduce the Block Diagram
Step-6: Analyze and Design
•The input signal is the desired position of
the antenna.
•Several common forms of input
functions are used for test purposes
Why Control Systems for CSE?
• Engineering involves the study of design and analysis
of engineering systems.
• Engineering systems are physical systems which could
be modeled mathematically (mathematical models).
• Many engineering or physical systems are control
systems.
Examples are: central heating system, auto pilot,
robots, automobiles, etc.
• Software engineers often participate in the development
of large softwares for control systems, e.g. software for
the control of the space shuttle.